The present invention relates to a liquid crystal projector which contains cooling means and in which noise due to a ventilation fan of the cooling means is reduced.
In a liquid crystal projector which magnifies and projects on a screen an image imaged on a liquid crystal panel, a high-illuminant high-voltage discharge lamp is used as a light source for illumination of a liquid crystal panel in order to obtain a high brightness projection image. The lamp emits high intensity thermal radiation, so, the vicinity of the lamp and the liquid crystal panel become high temperature, and an inner side of a housing of the liquid crystal projector (hereinafter, referred to as equipment housing) also becomes high temperature. Thus, the characteristics of each components may be adversely effected. Therefore, cooling means including a ventilation fan is provided in such a equipment housing, which, using the ventilation fan, intakes cool air from outside, passes it through the equipment housing, and exhausts it outside to radiate the heat generated in the equipment housing, outside.
In such a situation, if such cooling means is provided in the equipment housing, there has been a problem of noise occurring during use of the liquid crystal projector, because the hissing sound of the ventilation fan, or the sound of rotation of a motor driving the ventilation fan is emitted outside as a noise from an air exhaust port provided in the equipment housing. Conventionally, various methods for preventing such a noise have been proposed.
One of these methods involves setting ventilation fans to predetermined positions in the equipment housing to reduce noise emitted from an air intake port or an air exhaust port (for example, refer to JP-A-2002-40562).
Conventionally, the fan for air intake or air exhaust is provided near the air intake port or air exhaust port, but, in this method, these fans are provided apart from the air intake port or the air exhaust port by prescribed distances (for example, equal to or greater than the diameters of rotation portion of these ventilation fans multiplied by 0.4). In addition, ducts are provided between the air intake port and the air intake fan or between the air exhaust port and the air exhaust fan, and sound absorbing material on an inner surface of the ducts to further reduce the noise.
Another method proposed is to emit noise from the air exhaust port provided in the equipment housing, wherein the emitting direction can be set to any arbitrary direction (for example, refer to JP-A-2000-660306).
This method involves providing a duct in the air exhaust port on an external surface of the equipment housing, wherein the direction of the duct end can be changed. Thus, by turning the duct end to a direction where no viewer is present, air is exhausted and noise is also emitted in the direction so that no viewer would be bothered with noise.
Though the art described in JP-A-2002-40562 can reduce the noise of ventilation fans, since these ventilation fans, an air intake fan and air exhaust fan, are provided apart from the air intake port and the air exhaust port by prescribed distances, there are spaces in the equipment housing between the air intake fan and the air intake port on the inner side where the air intake port is provided, and also between the air exhaust fan and the air exhaust port on the inner side where the air exhaust port is provided. Such spaces are provided only for noise suppression, resulting in a large size of the equipment housing on account of only noise suppression. Therefore, when the liquid crystal projector is stored upon being unused, it requires larger storage space and also becomes bulky, being inconvenient to carry.
In addition, the art described in JP-A-2000-66306 can suppress noise without enlarging equipment housing itself, but, a duct is attached to the equipment housing with a shape protruding from the equipment housing, therefore, when the liquid crystal projector is stored or carried, the duct becomes an obstacle, so, the equipment being inconvenient.
An object of the present invention is to provide a liquid crystal projector which eliminates these problems, effectively reduces the noise emitted from cooling means, and can be small to be handled easily.